Known coin detectors and validators typically include a signal driving unit and a signal sensing unit. The driving unit and the sensing unit each typically include at least one coil formed on a solid core. The driving unit and the sensing unit are placed adjacent a coin path of the coin detector and validator.
In operation, a deposited coin is routed along the coin path. As the coin passes by the driving unit, the driving coil is energized with a known alternating signal. A varying magnetic field is generated by the driving coil when the coil is energized by such an alternating signal. As the coin passes through the varying magnetic field, eddy currents are induced in the coin. The eddy currents are generally concentrated near the surface of the coin and generate magnetic fields. The characteristics of the eddy current magnetic fields are dependent upon the resistance, inductance, and permeability of the coin material as well as the coin size.
The eddy current magnetic fields of the coin and the magnetic field generated by the driving coil induce a voltage in the sensing coil. The characteristics of the induced voltage are dependent on the magnetic fields from the driving unit and coin. Since the driving signal is known, the induced signal in the sensing coil can be analyzed to determine the coin type. For example, a matching algorithm can be used to match certain characteristics of the sensing coil signal with predetermined unique characteristics for each coin type. If the sensing unit signal matches certain characteristics for a particular coin type, then the deposited coin is identified as being that particular coin type.
Other known coin detectors include an integrated sensing and driving unit. An integrated sensing and driving unit includes one core. Both the sensing coil and the driving coil are formed on the one core.
Differential type sensing units with at least two sensing coils formed on one core also have been utilized in coin detectors. In differential type sensing units, the two sensing coils are wound on one core in a series opposing configuration. That is, the turns of the first coil are wound in one direction and the turns of the second coil are wound in an opposite direction. The differential type sensing unit may also be integrated with the driving unit. Particularly, two driving coils are formed on the one core over the sensing coils and in a series adding configuration.
Although differential type sensing units provide some advantages, known differential type sensing units are expensive to manufacture. Particularly, in manufacturing known differential type sensing units, the winding operation is a time-consuming process due to the need to prevent the loosening or unwinding of the first formed sensing coil while forming the second sensing coil. Such loosening or unwinding typically occurs when the winding direction is reversed in order to form the second sensing coil.
To prevent such loosening or unwinding, after the first sensing coil is formed, a glue or other adhesive is applied to the first sensing coil and allowed to cure. After the adhesive has cured, the second sensing coil is formed on another part of the core. The cured adhesive prevents the first sensing coil from loosening or unwinding as the second sensing coil is formed. Applying the adhesive and allowing it to cure is time-consuming and costly.
Further, it is desirable to utilize small sensing units in vending applications. The costs associated with forming differential type sensing units as described above, however, prevent economical manufacture of such small differential type sensing units. Small sensing units are desirable for coin detection because such small sensing units can be positioned close to the coin path for greater magnetic coupling with the coin passing along the coin path. Greater magnetic coupling results in higher magnitude signals being induced in the sensing coils and more accurate coin type identification.
In addition to the sensing unit size being a factor with respect to placement of the sensing unit in a desired position relative to the coin path, known differential type sensing units also include leads or wires extending from both ends of the core. Such a configuration inhibits the desired placement of the sensing unit in close proximity to the coin path. Particularly, with known configurations, at least one lead from the sensing unit extends from the end of the sensing unit which is placed adjacent the coin path. The lead interferes with positioning the sensing coil close to the coin path.
Also, known sensing units are coupled to other components by, for example, soldering the sensing unit leads to the leads of the other components. Soldering such leads together increases the assembly time and cost associated with such sensing units.
Accordingly, it is desirable and advantageous to provide a core for a differential type sensing unit so that the sensing unit can be inexpensively and quickly manufactured. It also is desirable and advantageous to provide a differential type sensing unit which is small in size and has leads configured so that the sensing unit can be positioned close to a coin path in a coin detector.
An object of the present invention is to provide a differential type sensing unit which can be easily and quickly manufactured.
Another object of the present invention is to provide a relatively small differential type sensing unit suitable for use in vending machine applications.
Still another object of the present invention is to provide a differential type sensing unit in which all of the leads extend from one end of the sensing unit core so that the other end of the sensing unit can be positioned close to a coin path.
Yet another object of the present invention is to provide a differential type sensing unit in which all of the leads or wires from such unit terminate in a connector block so that the sensing unit can be easily installed and replaced in various coin detectors.